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Wing tip shape? - 12/11/2007 6:00:19 PM   
Randy Etken



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Joined: 8/14/2002
From: Shakopee, MN, USA
Status: offline 		Ok you experts, which wing tip is the fastest at 180 mph??? The all white, red and yellow or all red?

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RE: Wing tip shape? - 12/11/2007 6:34:59 PM   
seanreit



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From: Cedar Park, TX, USA
Status: offline 		Of the three, the red, nothing is faster than nothing there at all

If the wing can be tapered to almost nothing and then flat on the end is even better. I fly Jets exclusively and all the fast ones taper down and are either rounded or squared off. But when you taper, you can afford to have aesthetically pleasing rounding of the wing tip.

Edit: in hindsight, because number two is heavily tapered or thinner than number three, it is faster. But I assumed we were talking shape, and not the actual wing.

< Message edited by seanreit -- 12/11/2007 6:54:54 PM >

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RE: Wing tip shape? - 12/11/2007 6:39:57 PM   
JCINTEXAS


 

Posts: 437
Joined: 3/23/2007
From: Smithville, TX, USA
Status: offline 		Randy,
This may not be an option on your plane,
but take a close look at the wingtip of the F-14 Tomcat,
It's "raked" so that the wing's trailing edge is slightly
longer than the leading edge. The tip is a slightly arced
line from LE to TE. This shape results in the lowest drag
at subsonic speeds. I agree with Sean, "Of the three, the red"
should be the fastest.
Regards
JC
www.topedge.com

http://www.topedge.com/panels/aircraft/sites/vf11/f-14size.gif

< Message edited by JCINTEXAS -- 12/11/2007 9:17:45 PM >

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RE: Wing tip shape? - 12/11/2007 6:52:27 PM   
highhorse


 

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From: Memphis, TN, USA
Status: offline 		I'll go w/ what's behind door # 2, Monty!

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RE: Wing tip shape? - 12/11/2007 7:24:04 PM   
Randy Etken



Posts: 258
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From: Shakopee, MN, USA
Status: offline 		They are all the same wing expect for tips.

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RE: Wing tip shape? - 12/12/2007 1:07:34 AM   
Randy Etken



Posts: 258
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From: Shakopee, MN, USA
Status: offline 		Also after take off plane is on 45 or 90 knife edge during whole race.

< Message edited by Randy Etken -- 12/12/2007 7:04:44 AM >

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RE: Wing tip shape? - 12/12/2007 2:01:23 AM   
seanreit



Posts: 6974
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From: Cedar Park, TX, USA
Status: offline 		Again, think of it in terms of what's "not there" is not drag. Look at all the fastest ships on the planet, what do their wing tips look like? High taper, no or little rounded tips. A good example of just a straight flat is this: http://www.aerospaceweb.org/aircraft/research/x15/

The smaller your wing area, the faster you are going to need to be going to create enough lift to stay in the air. I custom build a turbine F-20, and without it's wingrockets, it is a straight edged flat tip:

http://www.fas.org/man/dod-101/sys/ac/f-20_3view.gif

< Message edited by seanreit -- 12/12/2007 2:02:07 AM >

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RE: Wing tip shape? - 12/12/2007 1:35:48 PM   
Strat2003


 

Posts: 621
Joined: 3/9/2003
From: Mt. Pleasant, OH, AFGHANISTAN
Status: offline 		Waiiiiit a minute....is this another "Airplane on a Treadmill" question? "Fastest at 180 mph"? Aren't they all going the same speed at 180 mph?

Just being a wiseguy, lol

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RE: Wing tip shape? - 12/12/2007 8:49:50 PM   
banktoturn



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Randy,

At that speed, I'm assuming you would be on the straight, so induced drag is negligible. Under those conditions, you want a smooth, rounded tip, with no sharp edges and nothing squared off. There is no need to try to influence the tip vortex, you just want to avoid any sharp edges that could result in flow separation.

banktoturn

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RE: Wing tip shape? - 12/12/2007 9:09:00 PM   
js3



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Status: offline 		banktoturn,

But what about the turns where racers spend 30% of the heat?

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RE: Wing tip shape? - 12/12/2007 10:38:29 PM   
banktoturn



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Status: offline 		js3,

Good point. I took Randy's question to refer to the straight, but the best overall choice for pylon racing might need to account for induced drag in turns. I don't have data on the effectiveness of different tip shapes for induced drag reduction, but I tend to be a little skeptical of some of the claims I have seen. Winglets, if they are allowed, would be promising, but I don't know about other shapes, such as Hoerner tips.

If you really want to reduce induced drag, the tip shape is not the place to look.

banktoturn

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RE: Wing tip shape? - 12/12/2007 10:54:03 PM   
Randy Etken



Posts: 258
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From: Shakopee, MN, USA
Status: offline 		In a Q-500 pylon race the wing is at 90 degrees in turn one and 45 degrees the rest of the time. Only time straight is on take off. Race has 30 turns and 20 straight of 600 feet. Ten laps is 2 1/2 miles, record time is around 60 seconds.

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RE: Wing tip shape? - 12/12/2007 11:58:20 PM   
HighPlains


 

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quote:

If you really want to reduce induced drag, the tip shape is not the place to look.

I have to disagree. You want the maximum span of the wing at the trailing edge.

quote:

In a Q-500 pylon race the wing is at 90 degrees in turn one and 45 degrees the rest of the time. Only time straight is on take off. Race has 30 turns and 20 straight of 600 feet. Ten laps is 2 1/2 miles

I just not going to agree with any of this either. All the tight turns (making the turn at 2/3 as one turn) approach 90 degrees if one maintains altitude through the turn.

The so called "straight flight" which ties together the turns at both ends is also a turn (at a 45 degree bank) where the airplane would be doing roughly 1.4g to hold altitude. Since a 45 degree bank results in a turn with a radius of about 1950 at 170 mph. Depending on turn radius at pylon 1, the "straights" distance is only about 530 feet. However the bank of 45 degrees results in too short of distance by about 50 feet. So the bank needs to be slightly less (assuming calm conditions), about 42 degrees. On windy days (wind from pylon one) the bank from turn three to one is even less, while from one to two is greater due to variations in ground speed.

OK, nobody can fly that course perfectly and the difference in bank of a few degrees is very minor. But the reason you want to fly a course with 39 turns is that you can lower the amount of time spent in the high g turns at Pylon 1 and Pylons 2/3 by about 8%, which results in faster overall times.

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RE: Wing tip shape? - 12/13/2007 1:41:17 AM   
Randy Etken



Posts: 258
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From: Shakopee, MN, USA
Status: offline 		OK ,OK the question still is, what is the fastest wing tip for plyon racing of the three above?

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RE: Wing tip shape? - 12/13/2007 4:58:07 AM   
banktoturn



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Randy,

I can't make out all the details of the three wingtips very well. My answer is that the tip with the fewest sharp lines & sharp radii. It looks to me like #1 fits that bill.

banktoturn

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RE: Wing tip shape? - 12/13/2007 5:18:23 AM   
banktoturn



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Why do you want the maximum span at the trailing edge? Does this reduce induced drag?

By "straight", I mean the portions of the flight when the plane is not in a tight turn. Only during a tight turn is the coefficient of lift high enough to make induced drag a concern.

banktoturn


quote:

ORIGINAL: HighPlains

quote:

If you really want to reduce induced drag, the tip shape is not the place to look.

I have to disagree. You want the maximum span of the wing at the trailing edge.

quote:

In a Q-500 pylon race the wing is at 90 degrees in turn one and 45 degrees the rest of the time. Only time straight is on take off. Race has 30 turns and 20 straight of 600 feet. Ten laps is 2 1/2 miles

I just not going to agree with any of this either. All the tight turns (making the turn at 2/3 as one turn) approach 90 degrees if one maintains altitude through the turn.

The so called "straigh